Electromagnets are commonly used where there is a requirement for a magnetic field to be actuated (turned on/off).
An electromagnet achieves this effect by providing (generating) a magnetic field while electrical current is applied to it. To turn off the field the current is no longer applied to the electromagnet.
The use of electromagnets to effectuate magnetic fields suffers from one major drawback—the electromagnet requires a relatively large amount of electrical energy to operate.
Many techniques are being used to reduce the amount of external energy that an electromagnet requires. Primarily these techniques relate to the efficiency of the electromagnet and its components.